Temperature indicator



April 12, 1938. E. F. BACON.

TEMPERATURE INDICATOR Filed Feb. 27, 1935 m ma Apr-12,1938 ilEiSSUEi) FEB 18 1941 TEMPERATURE INDICATOR Elbrldge F. Bacon, Flint, Micln, asslgnor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application February 27, 1935, Serial No. 8,426

8 Claims.

' This invention relates to temperature indicators and has particular reference to the temperature indicators applied'to the internalcombustion engines used on automotive vehicles.

Internal combustion engines used on automotive vehicles are customarily supplied with a cooling system in which there is circulated a supply of water to keep the cylinders from overheating. It is desirable to know the temperature of the water in the cooling system for the reason that excessive temperatures of 200 indicate that the water is shortly to reach the boiling point and that the supply of water in the system needs to be replenished. For this reason temperature indicators are used-having a dial or signal at the dash board to indicate to the operator when the engine is being overheated or when the liquid in the system needs to be replenished.

In the present invention use is made of an elecno tric circuit having a signal or indicator at the dash board. In the circuit there is placed a resistor unit or plug secured in the engine block in contact with the water of the cooling system ;so that the unit or plug receives heat from the 25 water. The unit is a part of an electrical circuit and is equipped with a substance which'at low temperatures has a relatively high electrical resistance. but athigh temperatures, such as 180'; 200 or over, has a relatively low resistance. The

.30 Purpose of this substance is to prevent the opera- 4o Figure 1 shows aportion of an automobile with the heat indicator installed.-

Figure 2 is a. section through the unitor plug secured to the engine block.

Figure 3 is a section on line H of Figure 2.

Figure 4 is a section through the dash board showingthe signal at the dash.

, Figure 5 is a section through the dash board showing the switch. to operate the signal of Figure 4.

Referring to the drawing, the numeral 2 indicates an automotive vehicle as av whole. The vehicle has the usual hood 4, windshield 0, frame I, and engine ll. The engine has the usual head itand crankcase it. Associatedwiththeengineis, as the starting motor II and driven from the engine in the form of a square washer.

. exterior or threaded end I! of the bolt ll.

(01. so -es) is the usual transmission, the housing of which is indicated at is. The vehicle has the usual electrical battery which is grounded to the frame at 22. The usual instrument board is indicated at The resistor unit or plug 'of the invention is indicated as a whole at 28 and is shown in detail in Figures 2 and 3. The unit comprises the main body portion 28 having the hexagonal head 30 and the threads 32 to enable it to be applied to 10 the corresponding threaded portion It in the head I! of the engine block it. The body 28 is bored or hollow as indicated at 38 and has the bottom ll which is in contact with the water of the cooling system, one of the passages of which 15 is indicated at 40.

Interiorly of the bore 36 of the body It there is positioned the tube of insulating material 4 p which extends the entire length of the bore. At the bottom of the here there is positioned the 20 circular metal plate or washer 44 having the annular i'iange 4|. Over the plate there is positioned a quantity of boron ll and over the boron there is positioned a second metal plate It, a duplicate of the plate I4.

The head of the body II has the counterbore I! in which there is screwthreaded as at 84 the cup It. The cup I! has the squared portion I provided withan annular opening 00 at its center. The squared portion is shaped to form 30 a recess 02 at the inner portion of the cup 00 In the recess" there is received the electric insulation 04 and on the outside of the squared portion there is applied the electric insulation ll member ll in the form of a bolt is applied from the inside of the cup I! so that the bolt head 10 abuts against the insulation I but is out of contact with the cup. An enlarged portion II on the bolt closely ilts into corresponding opening 40 in the insulating washer l.

A-proiection It extends from the center of the head 10 toward the bore ll of the body ll, andm i, a spring 16 having a small end ll adjacent the projection 14 extends fromaround the proiection to the washer I. where the large end .0 of the spring contacts the washer I. to form an electrical circuit from the; washer 44 throu h theboron 4|, washer l0. spring II, and head It to the The usual metallic washer is applledvover the insulation 00 and a nut 00 is threaded on the threaded shank l2 rigidly and ;tightly to secure the parts together. A secondnnt O0 is threaded on the shank I! and rig dly clamps between the 58 A retaining as two nuts the end or terminal 90 of a wire 92 of the electrical circuit.

Referring to Figure 4, it will be seen that the signal is in the form of a lamp 94, but ifdesired an audible signal such as a hell or buzzer could be used. The lamp is secured in the usual lamp socket 96 which is held ina suitable thimble 98 secured by means of a flange I00 to the dash board 24. The thimble is open at its inner end as indicated at I02 to allow for the passage of the wires 92 and I04. The ends of the wires are suitably secured to a piece of insulation I06, and a spring I08 between the bottom of the thimble and the insulation I06 always urges the terminals IIO of the wires toward the terminals H2 of the lamp.

Referring to Figure 5, there is shown a conventional type of testing switch I I4. This switch has the, push button I I6 mounted in the housing H8 secured to the dash board 24 by means of the flange I20. A contact spring I22 always urges the push button II6 to the position shown in Figure 5 or away from the contact I24 and wire I26. The terminal I24 is held in the housing II8 by means of the insulating washer I28. A wire I29 leads from the switch I I4 to ground.

Referring to Figure 1, it will be seen that the circuit from the battery 20 includes .the wire I30 which leads to the ignition switch I32, the key of which is indicated at I34. The circuit is therefore open or closed depending on whether the ignition is open or closed, respectively. From the ignition switch I32 the wire I04 leads to the signal 94 and from the signal the wire 92 leads to the unit 26, the body of which is grounded to the frame through the engine block I0. It is therefore apparent that the signal 94 is not distinguishable at the dash unless the circuit indicated as a whole at I36 is closed through the unit 26 in the engine block. At lower temperatures of the water in the cooling system the resistance of the boron 48 is too great to allow sufiicient current to pass through the circuit properly to illuminate the signal 94. However, when higher temperatures are reached such as temperatures 180 or higher, sufficient current will pass through the boron to illuminate the light 94, and when temperatures as high as 212, or the boiling point of water, are reached, the resistance of the boron will be very low, such as approximately 2 ohms, so that the light 94 is brightly illuminated.

The boron 48 is not a pure boron owing to its cost and the difliculty of obtaining it. The boron is of an impure type or may have mixed therewith a certain quantity of aluminum, copper, or graphite to increase its conductivity. Pure boron oxidizes too readily and for this reason amorphous boron, which'can be produced from a reduction process from boric acid, is used. A resistor formed by assembling powdered boron with gilsonite under considerable pressure forms a satisfactory product to use in the resistor unit 26. Resistor units having 150 ohms resistance at room temperature and a very low resistance at high temperatures can be formed in this manner.

Instead of the light 94 (or a bell) a differential galvanometer or gauge such as shown in my Patents 1,791,786, February 10, 1931and 1,942,529, January 9, 1934, may be used. With a gauge of this type, the pointer will indicate a plurality of temperatures, the position of the needle over the scale being determined by the amount of current passing through the boron. The electrical resistance of the boron will depend onits temperature, and by suitably changing, calibrating and/ or proportioning the gauge or galvanometer coils to suit the range of resistance changes in the boron, the dial or scale of the gauge can be accurately divided properly to indicate the water temperature. The advantage of the gauge of my prior patents is that it gives a plurality of readings instead'of one, as will be the case with the light or bell.

I claim:

1. In a thermal resistor unit, a hollow resistor plug having a portion thereof in contact with the medium the thermal condition of which is to be determined, a quantity of boron in the plug, said boron being out of contact with the medium, means electrically to insulate said boron from the plug, and electrically conductive means at the ends of the quantity of boron to confine the boron and to complete an electric circuit therethrough.

2. In a thermal resistor unit, a hollow resistor plug having a portion thereof in contact with the medium the thermal condition of which is to be determined, a quantity of boron in the plug, said boron being out of contact with the medium, means electrically to insulate said boron from the plug, electrically conductive means at the ends of the quantity ofboron to confine the boron and to complete an electric circuit therethrough, a cup secured in one end of the plug, and an electrically conductive spring between the cup and said electrically conductive means.

3. In a thermal resistor unit -for application to a temperature indicating system, an integral hollow plug closed at one end and open at the other, said plug adapted to be secured in position on the device having the medium the temperature of which is to be determined, the closed end of said plug being inside the device and the open end outside thereof, thermal responsive means in the bottom of the plug at the closed end responsive to changes in temperature to enable an electric current to pass therethrough, means to insulate said thermal means from the plug, a removable cap in the open end of the .plug closing the open end, an electric contact secured to the cap, means to insulate the contact from the cap, and a compressed coil spring in the plug extending between the contact and the thermal responsive means in the plug and and in electrical contact with both, to enable an electric current to pass through the plug at higher temperatures.

4. In a thermal resistor unit for application to a temperature indicating system, an integral hollow plug closed at one end and open at the other, said plug adapted to be securedin position on the device having the medium the temperature of which is tobe detennined, the closed end of said plug being inside the device and the open end outside thereof, thermal responsive means in the bottom of the plug at the closed end responsive to changes in temperature to enable an electric current to pass therethrough, metallic electrically conducting plates at the ends of said thermal responsive means, means electrically to insulate one of said plates and said thermal responsive means from the-plug, a removable cap in the open end of the plug closing the open end, an electric contact secured to the cap, means to insulate the contact from the cap, and a compressed coil spring in the plug extending between the contact and the insulated plate in the plug end in electrical contact with both, to enable an electric current to pass through the plug at higher temperatures.

plug having a. portion thereof in contact with the medium the thermal-condition of which is to be determined, a quantity of boron in the plug, said boron being out of contact with the medium, means electrically to insulate said boron from the plug, electrical conducting members at both ends of the boron to hold the boron in place, and a spring between one of the members and one 'end of the plug to complete an electrical circuit.

ELBRIDGE F. BACON. 

